\begin{tikzpicture}[
    node distance = 2cm and 2cm,
    N/.style = {circle, draw, font=\Large, 
        minimum size=1.1em},
    every edge/.style = {draw, -> , semithick, shorten >=2pt},
    every edge quotes/.style = {auto=right, inner sep=2pt}
    ]
    \node[N] (1) [label=left :{+}] {1};
    \node[N] (2) [right of = 1] [label=right :{-}] {2};
    
    \path (1) edge [bend left, ->] node [above] {1} (2)
    (2) edge [bend left, ->] node [above] {1} (1)
    (1) edge [loop above] node [above] {0} ()
    (2) edge [loop above] node [above] {0} ();
\end{tikzpicture}
